The present invention is generally directed to toner processes, and, more specifically, to aggregation and coalescence processes for the preparation of toner compositions. In embodiments, the present invention is directed to the economical preparation of toners without pulverization and/or classification methods, and wherein toner compositions with an average volume diameter of from about 1 to about 25, preferably from 1 to about 10, and more preferably from about 3 to about 7 microns in average volume diameter, and narrow GSD of, for example, from about 1.16 to about 1.26 as measured on the Coulter Counter can be obtained. The resulting toners can be selected for known electrophotographic imaging and printing processes, including color processes, and lithography. In embodiments, the present invention is directed to a process comprised of dispersing a pigment, and optionally a charge control agent or additive in an aqueous mixture containing an ionic surfactant in an amount of from about 0.01 percent (weight percent throughout unless otherwise indicated) to about 10 percent, and shearing this mixture at high speeds, for example in the range of about 3,000 to about 15,000 rpm (revolutions per minute) and preferably in the range of from about 5,000 to about 12,000 rpm with a latex mixture comprised of suspended resin particles of from, for example, about 0.01 micron to about 1 micron in average volume diameter in an aqueous solution containing a counterionic surfactant in amounts of from about 0.01 percent to about 10 percent, and nonionic surfactant in an amount of from 0 and preferably 0.1 percent to about 5 percent, thereby causing a flocculation of resin particles, pigment particles and optional charge control particles, followed by heating at about 35.degree. to 5.degree. C., and preferably 20.degree. C. to 5.degree. C. below the resin Tg, which Tg range is generally between about 45.degree. C. to 85.degree. C., and preferably in the range of about 50.degree. C. to 75.degree. C. to form statically bound aggregates of from about 1 micron to about 10 microns in volume average diameter comprised of resin, pigment and optional toner additives like charge control additives. The flocculation or the heterocoagulation of the pigment particles containing ionic surfactant in amounts of about 0.01 percent to about 10 percent, and preferably between about 0.1 percent to about 5 percent with the latex is comprised primarily of resin particles and ionic surfactant mixture comprised of submicron resin particles containing the counterionic surfactant in the amounts of 0.01 percent to 10 percent and preferably between 0.1 percent to 5 percent causes a significant increase in the viscosity of the system, an increase, for example, of from about 4 centipoise to about 3,000 centipoise, resulting in large clusters or flocculants. Without the breakdown of these huge, large clusters or flocculants, a noncontrolled aggregation can be obtained resulting in particle size and GSD of unacceptable or undesirable values. By applying a high shear, for example about 3,000 to about 15,000 rpm and preferably between about 5,000 and 12,000 rpm during step (ii), a homogeneous or a uniform blend which has a whipped cream like consistency is obtained whereby the big clusters or flocculants are broken or reduced to about submicron size. This is followed by heating 30.degree. C. to 5.degree. C., and preferably 25.degree. C. to 5.degree. C. below the resin Tg, which resin Tg is generally in the range of 40.degree. C. to 80.degree. C., and preferably between about 50.degree. C. to about 75.degree. C. to form statically bound aggregates of step (iii) while stirring. The aforementioned increase in viscosity, for example from about 2 centipoise to about 2,000 centipoise, is not only caused by the pigment particles containing ionic surfactant with the latex mixture comprised of submicron resin particles containing the counterionic surfactant coming together, that is charge neutralization, but it is also a function of solids comprised of resin, pigment particles and optionally charge control agent (or volume fraction) loading in step (ii), for example at 20 percent loading, the viscosity can be as high as 10,000 centipoise. Also, the zeta potential of the latex prepared by emulsion polymerization containing resin particles in the anionic/nonionic surfactant can be another factor, for example a latex measured zeta potential of about -100 millivolts can require a larger quantity of the counterionic surfactant to that of the ionic surfactant in the latex for charge neutralization and hence flocculation to occur. Also, the amounts of the ionic to counterionic surfactants employed independent of the solids loading or the zeta potential of the latex can lead to an increase of viscosity, for example using 2:1 molar ratio of cationic to anionic surfactant increases the viscosity from about 2 to about 3,000 centipoise of the blend. With an increase in viscosity, it is important that a minimum shearing time is selected generally, for example, in the range of about 1 to about 60 minutes, and preferably in the range of about 2 to about 30 minutes in step (ii) to obtain a homogeneous, or uniform blend, which has a whipped cream like consistency. It is also important to stir the blend during the aggregation at an effective speed or tip speed during the aggregation step (iii), or it can result in undesired toner particle size and unwanted GSD.
The present invention is particularly directed to processes for correcting or partially reversing the electrostatically bound aggregates of undesired particle size and/or particle size distribution obtained when the blend comprised of latex, pigment optionally charge control agent from about 5 to 25 percent solids in water, and anionic/nonionic/cationic surfactants system has been heated below the resin Tg (step iii) where the resin Tg is generally in the range of 40.degree. C. to 85.degree. C., and preferably in the range of 50.degree. C. to 75.degree. C. by reshearing at a speed of 3,000 to 12,000 rpm (revolutions per minute) and preferably from about 5,000 to 10,000 rpm. The reshearing of the electrostatically bound aggregates of undesired particle size and/or GSD results in the generation of particles which are generally in the range of from about 0.8 to about 2.5 microns in average volume diameter. These particles in embodiments are smaller than the particles of between about 5 and about 20 microns in average volume diameter that can be obtained prior to reshearing. The reshearing not only, for example, creates a particle range of, for example, about 0.8 to about 2.5 microns, somewhere between the original starting materials, generally in the range of 0.05 to 0.4 micron, and 4 to 10 microns, but also creates a state from which aggregation can again be performed to achieve the desired toner particle size and a narrow toner GSD. The process of reshearing and reaggregation can be repeated many times, for example up to 10, providing, for example, that no final fusion or coalescence step (vii) of the electrostatically bound aggregates has occured. The reshearing is effective in breaking down the electrostatically bound aggregates providing the aggregation temperature in step (iii) is below the temperature where the resin begins to flow, thereby a fusion or coalescence has occured.
In another embodiment thereof, the present invention is directed to an in situ process comprised of first dispersing a pigment, such as HELIOGEN BLUE.TM. or HOSTAPERM PINK.TM., in an aqueous mixture containing a cationic surfactant, such as benzalkonium chloride (SANIZOL B-50.TM.), utilizing a high shearing device, such as a Brinkmann Polytron, a microfluidizer or sonicator; thereafter shearing at high speeds in the range of from about 3,000 to about 15,000 rpm, and preferably between 5,000 and 12,000 rpm this mixture with a latex of suspended resin particles, such as poly(styrene butadiene acrylic acid), poly(styrene butylacrylate acrylic acid) or PLIOTONE.TM., a poly(styrene butadiene), and which particles are, for example, of a size ranging from about 0.01 to about 0.5 micron in average volume diameter as measured by the Brookhaven nanosizer in an aqueous surfactant mixture containing an anionic surfactant, such as sodium dodecylbenzene sulfonate, for example NEOGEN R.TM. or NEOGEN SC.TM., and nonionic surfactant, such as alkyl phenoxy poly(ethylenoxy)ethanol, for example IGEPAL 897.TM. or ANTAROX 897.TM., thereby resulting in a flocculation, or heterocoagulation of the resin particles with the pigment particles; pumping the flocculated mixture through the shearing chamber, or zone at very high speeds generally in the range of 3,000 to 15,000 and preferably between 5,000 to 12,000 rpm; and continuously recirculating for from about 1 to about 120 minutes while being stirred at 200 rpm in a holding tank. This shearing action produces a homogeneous or a uniform blend, which has a whipped cream like consistency as opposed to a cottage cheese like consistency, normally achieved due to the lack of shearing. The length or the time of shearing and the type of consistency achieved is an important factor in determining the particle size and GSD when the aggregation of the blend is performed in step (iii). The blend comprises very small, submicron in size, thus is below about 1 micron, clusters of resin particles, pigment and optionally charge control agents, which particles are then allowed to grow by heating the mixture from about 25.degree. C. to about 5.degree. C. below the resin Tg, which resin Tg is preferably in the range of about 45.degree. C. to about 85.degree. C., and preferably in the range of about 50.degree. C. to about 75.degree. C. to speed up to 10 times, as described in copending application U.S. Ser. No. 082,660, the disclosure of which is totally incorporated herein by reference. The growth controlled of the aggregates can be accomplished while stirring at speed of about 150 to about 800 rpm or tip speed of about 80 centimeters/second to about 440 centimeters/second the components of (step iii). This results in the formation of statically bound aggregates ranging in size of from about 0.5 micron to about 10 microns in average diameter size as measured by the Coulter Counter (Multisizer II). When the stirring speed during the formation of the electrostatically bound aggregates in step (iii) is not sufficiently high, for example between about 50 and about 150 rpm corresponding to agitator tip speeds between 30 and 80 centimeters/second, or the length of time of shearing during the blending in step (ii) is not long enough or efficient, undesirable particles sized between 15 and 25 microns in diameter and/or particle size distribution with a GSD in the range of 1.30 to 100 can be obtained when measured on the Coulter Counter. At this stage, the temperature is lowered 10.degree. C. to 25.degree. C. below the resin Tg, which Tg is generally in the range of from about 40.degree. C. to about 85.degree. C. and preferably in the range of 50.degree. C. to 75.degree. C. Shearing is thereupon applied to the electrostatically bound aggregates of the undesired size and/or GSD obtained in step (iii) at speeds of from 3,000 to 15,000 rpm and preferably in the range of 5,000 to 12,000 rpm for a period of 1 to 20 minutes, resulting in breakdown of the aggregates (step iv). The particle size as measured on the Coulter Counter after shearing indicates a size range of from about 0.7 to about 2.5 microns.
The above sheared blend can then be reheated to temperatures of from about 25.degree. C. to about 5.degree. C. below the resin Tg, which resin Tg is preferably in the range of about 45.degree. C. to about 85.degree. C., and preferably in the range of 50.degree. C. to 75.degree. C., while being stirred for an effective period of time, for example from about 1 to about 6 hours, at an increased speed of from about 650 to 800 rpm, a tip speed of about 360 to about 440 centimeters/second, reference step (v). The growth and the GSD of the particles is periodically monitored by taking samples thereof and measuring them on the Coulter Counter. If the particle size or the GSD measured at this stage is not as desired, the process of reshearing and reaggregation can be repeated. Upon reaching acceptable or desired particle size and GSD, the stirring speed is reduced from 650 to 200 rpm corresponding to an agitator tip speed of from about 360 to about 110 centimeters/second followed by the addition of extra anionic or nonionic surfactant in the amount of from 0.5 to 5 percent by weight of water to stabilize or "freeze" the aggregate size and GSD formed in the previous steps. Thereafter, heating from about 5.degree. C. to about 50.degree. C. above the resin Tg, which resin Tg is in range of from about 50.degree. C. to about 75.degree. C. is accomplished to provide for particle fusion or coalescence of the polymer, or resin and pigment particles while being stirred; followed by washing with, for example, hot water to remove surfactant, and drying whereby toner particles comprised of resin and pigment with various particle size diameters can be obtained, such as from 1 to 12 microns in average volume particle diameter. The aforementioned toners are especially useful for the development of colored images with excellent line and solid resolution, and wherein substantially no background deposits are present. While not being desired to be limited by theory, it is believed that the flocculation or heterocoagulation is caused by the neutralization of the pigment mixture containing the pigment and cationic surfactant absorbed on the pigment surface with the resin mixture containing the resin particles and anionic surfactant absorbed on the resin particle. Furthermore, in other embodiments the ionic surfactants can be exchanged, such that the pigment mixture contains the pigment particle and anionic surfactant, and the suspended resin particle mixture contains the resin particles and cationic surfactant; followed by the ensuing steps as illustrated herein to enable flocculation by charge neutralization while shearing at high speed, generally in the range of 2,000 to 15,000 rpm and preferably in the range of 3,000 to 12,000 rpm to ensure a homogeneous, uniform or a whipped cream like blend comprised of small, submicron to 1 micron size, clusters or flocks, and thereby forming statically bound aggregate particles by stirring and heating (step iii) 5.degree. C. to 25.degree. C. below the resin Tg, which resin Tg is generally in the range of 45.degree. C. to 85.degree. C., and preferably between 50.degree. C. and 75.degree. C.; reshearing (step iv) whenever particle size and/or GSD is out of specification; reaggregating (v) to form the electrostatically bound aggregates by heating 5.degree. C. to 25.degree. C. below the resin Tg while stirring at the correct speed for a period of 1 to 6 hours to achieve desired particle size and narrow GSD; reducing the stirring speed from 650 to 200 rpm or a tip speed of from about 360 to 110 centimeters/second, and adding between 0.01 and 10 percent by weight of extra anionic/nonionic surfactant (step vi) to freeze the aggregate size achieved earlier; and heating the statically bound aggregates from about 5.degree. C. to about 50.degree. C. above the resin Tg (step vii) at temperatures of from 60.degree. C. to 100.degree. C. to form stable toner composite particles comprised of resin, pigment and optionally charge control agents. Of importance with respect to the processes of the present invention in embodiments, is the application of the high speed shearing devices normally comprised of rotator(s)-stator(s), for example polytrons, homogenizers, Megatrons, disintegrators; high efficiency dispensers and the like are crucial in step (ii) and step (iv) as illustrated herein to achieve a uniform blend initially and to reshear the particles that are out of specification in either particle size by being in the range of 10 to 30 microns in diameter, or out of specification in size distribution with GSDs of, for example, in the range from 1.0 to 100. The out of specification particle size and GSD of the electrostatically bound aggregates may be obtained, for example, when there is a lack of adequate stirring in step (iii). Material that is out of specification can be returned to a state wherein aggregation can once again be performed to achieve the desired particle size and a narrow particle size distribution, which generally is in the range of 1.18 to 1.27, by stirring from about 550 to 800 rpm corresponding to agitator tip speeds of from about 294 to 440 centimeters/second, and heating in step (v) at a temperature 25.degree. C. to 5.degree. C. below the resin Tg, which Tg is generally in the range of 40.degree. C. to 80.degree. C. and preferably between 50.degree. C to 75.degree. C., reducing the stirring speed from 650 to 200 rpm or tip speed from 360 to 110 centimeters/second, followed by the addition of extra anionic or nonionic surfactant in step (vi) in the amount of from 0.5 to 5 percent by weight of water to stabilize aggregates formed in the previous step (v) and, thereafter, heating 5.degree. C. to 50.degree. C. above the resin Tg in step (vii) to form stable toner composite particles comprised of resin and pigment particles with optionally charge control agent. By reshearing the out of specification particle size and GSD of the electrostatically bound aggregates obtained in step (iii) followed by reaggregation (step vi), the desired particle size and narrow particle size distribution resulted. Also, by reshearing the out of specification particle size and GSD of the electrostatically bound aggregates are eliminated or minimized.
In reprographic technologies, such as xerographic and ionographic devices, toners with average volume diameter particle sizes of from about 9 microns to about 20 microns are effectively utilized. Moreover, in some xerographic technologies, such as the high volume Xerox Corporation 5090 copier-duplicator, high resolution characteristics and low image noise are highly desired, and can be attained utilizing the small sized toners of the present invention with, for example, an average volume particle of from about 2 to 11 microns and preferably less than about 7 microns, and with narrow geometric size distribution (GSD) of from about 1.16 to about 1.3. Additionally, in some xerographic systems wherein process color is utilized, such as pictorial color applications, small particle size colored toners of from about 3 to about 9 microns are highly desired to avoid paper curling. Paper curling is especially observed in pictorial or process color applications wherein three to four layers of toners are transferred and fused onto paper. During the fusing step, moisture is driven off from the paper due to the high fusing temperatures of from about 130.degree. C. to about 160.degree. C. applied to the paper from the fuser. Where only one layer of toner is present, such as in black or in highlight xerographic applications, the amount of moisture driven off during fusing is reabsorbed proportionally by paper and the resulting print remains relatively flat with minimal curl. In pictorial color process applications wherein three to four colored toner layers are present, a thicker toner plastic level present after the fusing step inhibits the paper from sufficiently absorbing the moisture lost during the fusing step, and image paper curling results. These and other disadvantages and problems are avoided or minimized with the toners and processes of the present invention. It is preferable to use small toner particle sizes, such as from about 1 to 7 microns and with higher pigment loading, such as from about 5 to about 12 percent by weight of toner, such that the mass of toner layers deposited onto paper is reduced to obtain the same quality of image, and resulting in a thinner plastic toner layer onto paper after fusing, thereby minimizing or avoiding paper curling. Toners prepared in accordance with the present invention enable the use of lower fusing temperatures, such as from about 120.degree. C. to about 150.degree. C., thereby further avoiding or minimizing paper curl. Lower fusing temperatures minimize the loss of moisture from paper, thereby reducing or eliminating paper curl. Furthermore, in process color applications and especially in pictorial color applications, toner to paper gloss matching is highly desirable. Gloss matching is referred to as matching the gloss of the toner image to the gloss of the paper. For example, when a low gloss image of preferably from about 1 to about 30 gloss is desired, low gloss paper is utilized, such as from about 1 to about 30 gloss units as measured by the Gardner Gloss metering unit, and, which after image formation with small particle size toners of from about 3 to about 5 microns and fixing thereafter, results in a low gloss toner image of from about 1 to about 30 gloss units as measured by the Gardner Gloss metering unit. Alternatively, if higher image gloss is desired, such as from about above 30 to about 60 gloss units as measured by the Gardner Gloss metering unit, higher gloss paper is utilized, such as from about above 30 to about 60 gloss units, and, which after image formation with small particle size toners of the present invention of from about 3 to about 5 microns and fixing thereafter, results in a higher gloss toner image of from about above 30 to about 60 gloss units as measured by the Gardner Gloss metering unit. The aforementioned toner to paper matching can be attained with small particle size toners, such as less than 7 microns and preferably less than 5 microns, such as from about 1 to about 4 microns, such that the pile height of the toner layer(s) is considered low.
Numerous processes are known for the preparation of toners, such as, for example, conventional processes wherein a resin is melt kneaded or extruded with a pigment, micronized and pulverized to provide toner particles with an average volume particle diameter of from about 9 microns to about 20 microns and with broad geometric size distribution of from about 1.4 to about 1.7. In such processes, it is usually necessary to subject the aforementioned toners to a classification procedure, such that the geometric size distribution of from about 1.2 to about 1.4 is attained. Also, in the aforementioned conventional process, low toner yields after classifications may be obtained. Generally, during the preparation of toners with average particle size diameters of from about 11 microns to about 15 microns, toner yields range from about 70 percent to about 85 percent after classification. Additionally, during the preparation of smaller sized toners with particle sizes of from about 7 microns to about 11 microns lower toner yields are obtained after classification, such as from about 50 percent to about 70 percent. With the processes of the present invention in embodiments, small average particle sizes of, for example, from about 3 microns to about 9 microns, and preferably 5 microns are attained without resorting to classification processes, and wherein narrow geometric size distributions are attained, such as from about 1.16 to about 1.30, and preferably from about 1.16 to about 1.25. High toner yields are also attained such as from about 90 percent to about 98 percent in embodiments. In addition, by the toner particle preparation process of the present invention in embodiments, small particle size toners of from about 3 microns to about 7 microns can be economically prepared in high yields such as from about 90 percent to about 98 percent by weight based on the weight of all the toner material ingredients, such as toner resin and pigment.
There is illustrated in U.S. Pat. No. 4,996,127 a toner of associated particles of secondary particles comprising primary particles of a polymer having acidic or basic polar groups and a coloring agent. The polymers selected for the toners of the '127 patent can be prepared by an emulsion polymerization method, see for example columns 4 and 5 of this patent. In column 7 of this '127 patent, it is indicated that the toner can be prepared by mixing the required amount of coloring agent and optional charge additive with an emulsion of the polymer having an acidic or basic polar group obtained by emulsion polymerization. Also, in column 9, lines 50 to 55, it is indicated that a polar monomer, such as acrylic acid in the emulsion resin, is necessary, and toner preparation is not obtained without the use, for example, of an acrylic acid polar group. The process of the present invention need not utilize polymer polar acid groups, and toners can be prepared with resins, such as poly(styrene-butadiene) or PLIOTONE.TM., containing no polar acid groups. Additionally, the process of the '127 patent does not appear to utilize counterionic surfactant and flocculation process as does the present invention, and does not appear to use a counterionic surfactant for dispersing the pigment. In U.S. Pat. No. 4,983,488 is illustrated a process for the preparation of toners by the polymerization of a polymerizable monomer dispersed by emulsification in the presence of a colorant and/or a magnetic powder to prepare a principal resin component, and then effecting coagulation of the resulting polymerization liquid in such a manner that the particles in the liquid after coagulation have diameters suitable for a toner. It is indicated in column 9 of this patent that coagulated particles of 1 to 100, and particularly 3 to 70 are obtained. This process is thus directed to the use of coagulants, such as inorganic magnesium sulfate, which results in the formation of particles with wide GSD. Furthermore, the '488 patent does not, it is believed, disclose the process of counterionic, for example controlled aggregation is obtained by changing the counterionic strength flocculation as with the present invention. The disadvantages, for example poor GSD are obtained, hence, classification is required resulting in low yields, are illustrated in U.S. Pat. No. 4,797,339, wherein there is disclosed a process for the preparation of toners by resin emulsion polymerization, wherein similar to the '127 patent polar resins of oppositely charges are selected, and wherein flocculation as in the present invention is not disclosed; and U.S. Pat. No. 4,558,108, wherein there is disclosed a process for the preparation of a copolymer of styrene and butadiene by specific suspension polymerization. Other prior art that may be of interest includes U.S. Pat. Nos. 3,674,736; 4,137,188 and 5,066,560.
The process described in the present application has advantages over processes with reshearing and freezing in that although one may attain a uniform and homogeneous blend having a whipped cream like consistency during step (ii) other auxiliary equipment, such as stirrer breakdown, loss in temperature control, loss of stirrer speed control, build up of viscosity, and the like result during the formation of electrostatically bound aggregates (step iii), resulting in out of specification particle size and/or GSD. By reshearing (step iv) and reaggregating (step v), one can obtain the desired particle size and narrow GSD without any loss in productivity. This recovery in product is important since it not only eliminates or reduces the loss of product, but also eliminates the additional incurred costs of waste disposal, rendering the process environmentally friendly. Moreover, the process of reshearing and reaggregation allows for changes in terms of particle size and GSD during the process, and allows for correction in the event the wrong quantities of starting materials, for example water, cationic (flocculating) agent, or latex, were added, which when monitored in terms of particle size or GSD can be resheared and reaggregated.
In copending patent application U.S. Ser. No. 082,651, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of toner compositions with controlled particle size comprising:
(i) preparing a pigment dispersion in water, which dispersion is comprised of pigment, an ionic surfactant and an optional charge control agent; PA1 (ii) shearing at high speeds the pigment dispersion with a polymeric latex comprised of resin, a counterionic surfactant with a charge polarity of opposite sign to that of said ionic surfactant, and a nonionic surfactant thereby forming a uniform homogeneous blend dispersion comprised of resin, pigment, and optional charge agent; PA1 (iii) heating the above sheared homogeneous blend below about the glass transition temperature (Tg) of the resin while continuously stirring to form electrostatically bound toner size aggregates with a narrow particle size distribution; PA1 (iv) heating the statically bound aggregated particles above about the Tg of the resin particles to provide coalesced toner comprised of resin, pigment and optional charge control agent, and subsequently optionally accomplishing (v) and (vi); PA1 (v) separating said toner; and PA1 (vi) drying said toner. PA1 (i) preparing by emulsion polymerization an anionic charged polymeric latex of submicron particle size, and comprised of resin particles and anionic surfactant; PA1 (ii) preparing a dispersion in water, which dispersion is comprised of optional pigment, an effective amount of cationic flocculant surfactant, and optionally a charge control agent; PA1 (iii) shearing the dispersion (ii) with said polymeric latex thereby causing a flocculation or heterocoagulation of the formed particles of optional pigment, resin and charge control agent to form a high viscosity gel in which solid particles are uniformly dispersed; PA1 (iv) stirring the above gel comprised of latex particles, and oppositely charged dispersion particles for an effective period of time to form electrostatically bound relatively stable toner size aggregates with narrow particle size distribution; and PA1 (v) heating the electrostatically bound aggregated particles at a temperature above the resin glass transition temperature (Tg) thereby providing said toner composition comprised of resin, optional pigment and optional charge control agent. PA1 (i) preparing a pigment dispersion in water, which dispersion is comprised of a pigment, an ionic surfactant in amounts of from about 0.5 to about 10 percent by weight of water, and an optional charge control agent; PA1 (ii) shearing the pigment dispersion with a latex mixture comprised of a counterionic surfactant with a charge polarity of opposite sign to that of said ionic surfactant, a nonionic surfactant and resin particles, thereby causing a flocculation or heterocoagulation of the formed particles of pigment, resin and charge control agent; PA1 (iii) stirring the resulting sheared viscous mixture of (ii) at from about 300 to about 1,000 revolutions per minute to form electrostatically bound substantially stable toner size aggregates with a narrow particle size distribution; PA1 (iv) reducing the stirring speed in (iii) to from about 100 to about 600 revolutions per minute and subsequently adding further anionic or nonionic surfactant in the range of from about 0.1 to about 10 percent by weight of water to control, prevent, or minimize further growth or enlargement of the particles in the coalescence step (iii); and PA1 (v) heating and coalescing from about 5.degree. to about 50.degree. C. above about the resin glass transition temperature, Tg, which resin Tg is from between about 45.degree. to about 90.degree. C. and preferably from between about 50.degree. and about 80.degree. C., the statically bound aggregated particles to form said toner composition comprised of resin, pigment and optional charge control agent. PA1 (i) preparing a pigment dispersion in water, which dispersion is comprised of pigment, ionic surfactant, and optionally a charge control agent; PA1 (ii) shearing the pigment dispersion with a polymeric latex comprised of resin of submicron size, a counterionic surfactant with a charge polarity of opposite sign to that of said ionic surfactant and a nonionic surfactant thereby causing a flocculation or heterocoagulation of the formed particles of pigment, resin and charge control agent, and generating a uniform blend dispersion of solids of resin, pigment, and optional charge control agent in the water and surfactants; PA1 (iii) (a) continuously stirring and heating the above sheared blend to form electrostatically bound toner size aggregates; or PA1 (iii) (b) further shearing the above blend to form electrostatically bound well packed aggregates; or PA1 (iii) (c) continuously shearing the above blend, while heating to form aggregated flake-like particles; PA1 (iv) heating the above formed aggregated particles about above the Tg of the resin to provide coalesced particles of toner; and optionally PA1 (v) separating said toner particles from water and surfactants; and PA1 (vi) drying said toner particles. PA1 (i) preparing a pigment dispersion, which dispersion is comprised of a pigment, an ionic surfactant, and optionally a charge control agent; PA1 (ii) shearing said pigment dispersion with a latex or emulsion blend comprised of resin, a counterionic surfactant with a charge polarity of opposite sign to that of said ionic surfactant and a nonionic surfactant; PA1 (iii) heating the above sheared blend below about the glass transition temperature (Tg) of the resin to form electrostatically bound toner size aggregates with a narrow particle size distribution; and PA1 (iv) heating said bound aggregates above about the Tg of the resin. PA1 (i) preparing a pigment dispersion in water, which dispersion is comprised of pigment, a counterionic surfactant with a charge polarity of opposite sign to the anionic surfactant of (ii) and optionally a charge control agent; PA1 (ii) shearing the pigment dispersion with a latex comprised of resin, anionic surfactant, nonionic surfactant, and water; and wherein the latex solids content, which solids are comprised of resin, is from about 50 weight percent to about 20 weight percent thereby causing a flocculation or heterocoagulation of the formed particles of pigment, resin and optional charge control agent; diluting with water to form a dispersion of total solids of from about 30 weight percent to 1 weight percent, which total solids are comprised of resin, pigment and optional charge control agent contained in a mixture of said nonionic, anionic and cationic surfactants; PA1 (iii) heating the above sheared blend at a temperature of from about 5.degree. C. to about 25.degree. C. below about the glass transition temperature (Tg) of the resin while continuously stirring to form toner sized aggregates with a narrow size dispersity; and PA1 (iv) heating the electrostatically bound aggregated particles at a temperature of from about 5.degree. to about 50.degree. C. above about the Tg of the resin to provide a toner composition comprised of resin, pigment and optionally a charge control agent. PA1 (i) preparing a pigment dispersion in a water, which dispersion is comprised of a pigment, an ionic surfactant and optionally a charge control agent; PA1 (ii) shearing the pigment dispersion with a latex mixture comprised of a counterionic surfactant with a charge polarity of opposite sign to that of said ionic surfactant, a nonionic surfactant and resin particles, thereby causing a flocculation or heterocoagulation of the formed particles of pigment, resin and charge control agent to form electrostatically bound toner size aggregates; and PA1 (iii) heating the statically bound aggregated particles above the Tg to form said toner composition comprised of polymeric resin, pigment and optionally a charge control agent. PA1 (i) preparing a pigment dispersion in water, which dispersion is comprised of pigment, an ionic surfactant, and an optional charge control agent; PA1 (ii) shearing the pigment dispersion with a polymeric latex comprised of resin, a counterionic surfactant with a charge polarity of opposite sign to that of said ionic surfactant, and which dispersion also contains a nonionic surfactant thereby forming a homogeneous or a uniform blend dispersion of flocs comprised of resin, pigment, and optional charge additive; PA1 (iii) heating the above sheared homogeneous blend below the glass transition temperature (Tg) of the resin, and wherein the resin Tg is in the range of about 40.degree. C. to about 85.degree. C., and preferably in the range of about 50.degree. C. to about 75.degree. C. to form electrostatically bound toner size aggregates with an average volume diameter of from about 3 to about 10 microns and a particle size distribution of between 1.10 and 1.30; PA1 (iv) reshearing the above electrostatically bound toner aggregates (iii) at a speed of from about 3,000 to about 15,000 revolutions per minute for a period of from about 1 to about 60 minutes to fragment or break down the toner aggregates of (iii) into smaller average diameter particle size in the range of from about 0.5 to about 2 microns to allow reaggregation (step v) of said fragment particles; PA1 (v) heating the resulting formed sheared homogeneous blend (iv) comprised of resin, pigment particles, toner additives, and surfactants in water below the glass transition temperature (Tg) of the resin while continuously stirring at about 450 to about 800 revolutions per minute, corresponding to an agitator tip speed of between 240 to about 440 centimeters per second to form electrostatically bound toner size aggregates with a narrow particle size distribution; PA1 (vi) adding further ionic or nonionic surfactant in an amount of from about 0.1 to about 10 percent by weight of water to control, prevent, or minimize further growth or enlargement of the particles in the coalescence step (vii); PA1 (vii) heating the formed statically bound aggregated particles of (vi) above the Tg of the resin to provide coalesced particles of toner comprised of resin, pigment and optional charge control agent; and optionally PA1 (viii) separating the toner; and PA1 (ix) drying the toner. PA1 (i) preparing a pigment dispersion in water, which dispersion is comprised of a pigment in an ionic surfactant; PA1 (ii) shearing the pigment dispersion with a polymeric latex comprised of resin of submicron size in the range of from about 0.1 to about 1 micron average volume diameter, a counterionic surfactant with a charge polarity of opposite sign to that of said ionic surfactant and a nonionic surfactant thereby resulting in a uniform homogeneous blend of flocs with particles of less than or equal to from about 0.5 to about 1 micron in average volume diameter, and which particles are comprised of resin and pigment; PA1 (iii) heating the above sheared homogeneous blend below, from about 25.degree. C. to about 5.degree. C., the glass transition temperature (Tg) of the resin and wherein the Tg of the resin is in the range of from about 40.degree. C. to about 85.degree. C. and preferably in the range of from about 50.degree. C. to about 75.degree. C., while continuously stirring at from about 200 to about 1,000 rpm, or tip speeds from about 110 to about 534 centimeters/second and preferably from about 300 to about 700 revolutions per minute (rpm), or tip speeds of from about 160 to about 373 centimeters/second to form electrostatically bound toner size aggregates; PA1 (iv) reshearing the aggregates formed in step (iii) at speed of from between about 3,000 to about 10,000 rpm for a period of from about 1 minute to about 60 minutes and preferably for a period of from about 2 to about 30 minutes; PA1 (v) heating the above resheared blend at about or below, from about 25.degree. C. to about 5.degree. C., the glass transition temperature (Tg) of the resin and wherein the Tg of the resin is in the range of from about 40.degree. C. to about 85.degree. C. and preferably in the range of from about 50.degree. C. to about 75.degree. C., while continuously stirring at from about 200 to about 1,000, or tip speeds from about 110 to about 534 centimeters/second and preferably from about 450 to about 800 revolutions per minute (rpm), or tip speeds of from about 240 to about 440 centimeters/second to form electrostatically bound toner size aggregates with narrow GSD; PA1 (vi) reducing the stirring to about 200 rpm, or a tip speed to 110 centimeters/second, followed by adding additional anionic or nonionic surfactant, about 0.02 percent to about 5 percent by weight of water, to freeze or retain the size and GSD of the aggregates achieved in step (v); and PA1 (vii) heating, for example, at temperatures of about 60.degree. C. to about 105.degree. C., the statically bound aggregated particles above the resin Tg, which Tg is generally in the range of about 40.degree. C. to about 85.degree. C. and preferably in the range of about 50.degree. C. to about 75.degree. C. to provide coalesced particles of a toner composition comprised of polymeric resin, pigment and optionally a charge control agent; PA1 (i) preparing a pigment dispersion in water, which dispersion is comprised of a pigment of a diameter of from about 0.01 to about 0.3 micron, and an ionic surfactant; PA1 (ii) shearing the pigment dispersion with a latex blend comprised of resin of submicron size of from about 0.01 to about 1 micron, a counterionic surfactant with a charge polarity, positive or negative, and of opposite sign to that of the ionic surfactant and a nonionic surfactant, thereby causing a flocculation or heterocoagulation of the formed particles of pigment, resin and charge control agent to form a uniform dispersion of solids in water and the anionic/nonionic/cationic surfactants; PA1 (iii) heating the above sheared blend at a temperature of from about 25.degree. C. to about 5.degree. C. below the resin Tg, which resin Tg is generally in the range of about 40.degree. C. to about 80.degree. C. and preferably between about 50.degree. C. and about 75.degree. C., while continuously stirring to form electrostatically bound, relatively stable, for Coulter Counter measurements, toner size aggregates; PA1 (iv) reshearing the aggregates formed in step (iii) at speeds of about 3,000 to about 10,000 rpm for a period of 1 to 60 minutes and preferably for a period of 2 to 30 minutes to enable the out of specification particles to, for example, be recycled; PA1 (v) heating the above resheared blend below, from about 25.degree. C. to about 5.degree. C., the glass transition temperature (Tg) of the resin and wherein the Tg of the resin is in the range of from about 40.degree. C. to about 85.degree. C. and preferably in the range of from about 50.degree. C. to about 75.degree. C., while continuously stirring at from about 200 to about 1,000 rpm, or tip speeds of from about 110 to about 534 centimeters/second and preferably from about 450 to about 800 revolutions per minute (rpm), or tip speeds of from about 240 to about 440 centimeters/second to form electrostatically bound toner size aggregates with a desired narrow GSD; PA1 (vi) reducing the stirring speed and then adding extra anionic or nonionic surfactant, about 0.02 percent to about 5 percent by weight of water, to freeze or retain the size and GSD of those aggregates achieved in step (v); PA1 (vii) heating the statically bound aggregated particles at a temperature of from about 5.degree. C. to about 50.degree. C. above the resin Tg, which resin Tg is generally in the range of about 40.degree. C. to about 80.degree. C. and preferably between about 50.degree. C. and about 75.degree. C. to provide mechanically stable toner particles comprised of polymeric resin, pigment and optionally a charge control agent; PA1 (viii) separating the toner particles by filtration; and PA1 (ix) drying the toner particles; and PA1 (i) preparing a pigment dispersion in water, which dispersion is comprised of a pigment and an ionic surfactant; PA1 (ii) shearing the pigment dispersion with a latex blend comprised of resin particles of submicron size, a counterionic surfactant with a charge polarity of opposite sign to that of said ionic surfactant and which blend contains a nonionic surfactant thereby causing a flocculation or heterocoagulation of the formed particles of pigment and resin to form a uniform dispersion of solids of resin and pigment in the water, and surfactants; PA1 (iii) heating the above sheared blend below the glass transition temperature (Tg) of the resin particles, while continuously stirring to form electrostatically bound toner size aggregates; and PA1 (iv) reshearing the aggregates formed in step (iii) at speeds of from about 3,000 to about 10,000 rpm for a period of 1 to 60 minutes and preferably for a period of 2 to 30 minutes; PA1 (v) heating the above resheared blend at about or below, from about 25.degree. C. to about 5.degree. C., the glass transition temperature (Tg) of the resin and wherein the Tg of the resin is in the range of from about 40.degree. C. to about 85.degree. C. and preferably in the range of from about 50.degree. C. to about 75.degree. C., while continuously stirring at from about 200 to about 1,000 rpm, or tip speeds from about 110 to about 534 centimeters/second and preferably from about 450 to about 800 revolutions per minute (rpm), or tip speeds from about 240 to about 440 centimeters/second to form electrostatically bound toner size aggregates with narrow GSD; PA1 (vi) reducing the stirring speed and then adding extra anionic or nonionic surfactant, about 0.02 percent to about 5 percent by weight of water, to retain the size and GSD of the aggregates achieved in step (v); and PA1 (vii) heating the statically bound aggregated particles at about or above the resin Tg, which Tg is in range of from about 40.degree. C. to about 80.degree. C. and preferably from about 50.degree. C. to about 75.degree. C. to provide a toner composition comprised of polymeric resin, and pigment. PA1 (i) preparing a pigment dispersion in water, which dispersion is comprised of a pigment, and an ionic surfactant; PA1 (ii) shearing at high speeds the pigment dispersion with a latex mixture comprised of a counterionic surfactant with a charge polarity of opposite sign to that of said ionic surfactant, a nonionic surfactant and resin particles to achieve a homogeneous or uniform blend comprised of resin particles, and pigment particles in water and the above surfactant mixtures; PA1 (iii) stirring in the range of from about 200 to about 1,000 rpm, or tip speeds of from about 110 to about 534 centimeters/second, or tip speeds of from about 240 to about 440 centimeters/second and preferably in the range of 300 to 700 rpm, or tip speeds of from about 160 to about 373 centimeters/second, for about 1 to 4 hours, the homogenized mixture with optional heating at a temperature of from about 25.degree. C. to about 50.degree. C., and below about 25.degree. C. to about 5.degree. C., the resin Tg, which resin Tg is in the range of about 45.degree. C. to about 85.degree. C. and preferably between about 50.degree. C. and about 75.degree. C., thereby causing a flocculation or heterocoagulation of the formed particles of pigment, and resin and to form electrostatically bound toner size aggregates; PA1 (iv) reshearing the aggregates formed in step (iii) at speeds of 3000 to 10,000 rpm for a period of 1 to 60 minutes and preferably for a period of 2 to 30 minutes; PA1 (v) heating the above resheared blend below, from about 25.degree. C. to about 5.degree. C., the glass transition temperature (Tg) of the resin and wherein the Tg of the resin is in the range of from about 40.degree. C. to about 85.degree. C. and preferably in the range of from about 50.degree. C. to about 75.degree. C., while continuously stirring at from about 200 to about 1,000, or tip speeds from about 110 to about 534 centimeters/second and preferably from about 450 to about 800 revolutions per minute (rpm), or tip speeds of from about 240 to about 440 centimeters/second to form electrostatically bound toner size aggregates with narrow GSD; PA1 (vi) reducing the stirring speed and then adding extra anionic or nonionic surfactant, about 0.02 percent to about 5 percent by weight of water, to freeze or retain the size and GSD of those aggregates achieved in step (v); PA1 (vii) stabilizing the formed aggregates by the addition of extra 0.5 to 10 percent of the total kettle volume of anionic or nonionic surfactant prior to heating above the resin Tg, which resin Tg is in the range of about 45.degree. C. to about 8.degree. C. and preferably between about 50.degree. C. and about 75.degree. C.; and PA1 (viii) heating to from about 60.degree. C. to about 95.degree. C. the statically bound aggregated particles, for example about 5.degree. C. to about 50.degree. C. above the resin Tg, which resin Tg (glass transition temperature) is in the range of between about 50.degree. C. to about 80.degree. C. and preferably between about 50.degree. C. to about 75.degree. C. to form a toner composition comprised of polymeric resin, and pigment.
In copending patent application U.S. Ser. No. 083,146, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of toner compositions with a volume median particle size of from about 1 to about 25 microns, which process comprises:
In copending patent application U.S. Ser. No. 083,157, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of toner compositions with controlled particle size comprising:
In copending patent application U.S. Ser. No. 082,741, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of toner compositions with controlled particle size and selected morphology comprising
In copending patent application U.S. Ser. No. 082,660, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of toner compositions comprising:
In copending patent application U.S. Ser. No. 083,116, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of toner compositions comprising
In U.S. Pat. No. 5,290,654, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of toners comprised of dispersing a polymer solution comprised of an organic solvent, and a polyester and homogenizing and heating the mixture to remove the solvent and thereby form toner composites. Additionally, there is disclosed in U.S. Pat. No. 5,278,520, the disclosure of which is totally incorporated herein by reference, a process for the preparation of in situ toners comprising an halogenization procedure which chlorinates the outer surface of the toner and results in enhanced blocking properties. More specifically, this patent application discloses an aggregation process wherein a pigment mixture containing an ionic surfactant is added to a resin mixture containing polymer resin particles of less than 1 micron, nonionic and counterionic surfactant, and thereby causing a flocculation which is dispersed to statically bound aggregates of about 0.5 to about 5 microns in volume diameter as measured by the Coulter Counter, and thereafter heating to form toner composites or toner compositions of from about 3 to about 7 microns in volume diameter and narrow geometric size distribution of from about 1.2 to about 1.4, as measured by the Coulter Counter, and which exhibit, for example, low fixing temperature of from about 125.degree. C. to about 150.degree. C., low paper curling, and image to paper gloss matching.
In U.S. Pat. No. 5,308,734, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of toner compositions which comprises generating an aqueous dispersion of toner fines, ionic surfactant and nonionic surfactant, adding thereto a counterionic surfactant with a polarity opposite to that of said ionic surfactant, homogenizing and stirring said mixture, and heating to provide for coalescence of said toner fine particles.
In copending patent application, U.S. Ser. No. 022,575, the disclosure of which is totally incorporated herein by reference, there is disclosed a process for the preparation of toner compositions comprising
There are believed to be a number of advantages of the present invention as indicated herein, for example, although in many instances these can be attained a homogeneous or uniform blend in an initial blending step (ii) when equipment, operational fault, or error occurs during the execution of the process, there can be obtained out of specification material in terms of particle size and GSD due to breakdown of the stirrer, loss of temperature control or lack of efficient mixing, and by reshearing and reaggregating the material that does not conform to specification, the formation of toners with the desired particle size having a narrow GSD, thereby preventing loss of material and additional incurred cost of waste disposal results. Also, the process of the present invention allows the targeted size and GSD of the final toner to be changed while the process is proceeding provided the aggregates have not been finally coalesced or fused into the final toner form by heating above the Tg of the resin.